A European spacecraft confirmed a report on the release of methane from the surface of Mars.
The methane peak was measured for the first time by NASA's Curiosity rover on the surface; Now it has been confirmed by the Mars Express orbiter.
The nature and extent of methane in the Martian atmosphere is intensely debated.
Gas is of interest because terrestrial methane can be produced by life forms, as well as by geological processes.
It is badumed that methane only has a very short life in the Martian atmosphere, so detecting it means that it must have been released very recently.
The Curiosity rover measured a strong methane signal on June 15, 2013.
The measurement was confirmed in the data collected the next day by the Planetary Fourier Spectrometer (PFS) aboard the Mars Express.
The results of two studies are described in the journal Nature Geoscience.
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"In general, we did not detect any methane, apart from a definitive detection of approximately 15 parts per billion by volume of methane in the atmosphere, which turned out to be a day after Curiosity reported an increase of approximately six parts per billion," Marco says. Giuranna, principal investigator of the PFS.
"Although the parts per billion in general mean a relatively small amount, it is quite remarkable for Mars, our measure corresponds to an average of about 46 tons of methane that was present in the area of 49,000 square kilometers observed from our orbit."
At the time Curiosity was detected, it was thought that the methane could have originated north of the rover (because the prevailing winds were to the south) and that the release came from inside the Gale crater, the Curiosity landing site.
The team conducted two independent badyzes to determine the possible regions of methane origin, dividing a wide region around the Gale crater into grids of approximately 250 by 250 square kilometers.
Biology or geology?
There are a variety of ways in which methane can be produced on Mars.
If there are still microbes, they are a possible source. Methane produced by microorganisms in the distant past could also be trapped in the ice. When the ice melts, it could release the old methane into the atmosphere.
But there are geological processes that can produce methane and do not require biology. These include serpentinization, a process of mineral alteration in the crust that involves heat and water. Methane can be manufactured as a subsequent product of serpentinization.
Marco Giuranna suspects that the feather did not originate in Gale Crater.
The scientists examined the region around Gale for features where a gas leak is expected.
It is known that this process on Earth occurs along tectonic faults and natural gas fields.
"We identify tectonic faults that could extend below a proposed region to contain shallow ice." Since permafrost is an excellent seal for methane, it is possible that ice here can trap subsurface methane and release it episodically throughout the faults that break this ice, "said Giuseppe Etiope of the National Institute of Geophysics and Volcanology in Rome, co-author of one of the studies.
"Notably, we saw that atmospheric simulation and geological badessment, conducted independently, suggested the same region of methane origin."
The ExoMars Trace Gas Orbiter, which is designed to make a detailed inventory of the Martian atmosphere, was launched in 2016. However, it has yet to report its scientific results.